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Microsoft Exchange Online outage affecting global users

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📰 1 unique sources, 1 articles

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Microsoft mitigated an Exchange Online outage that affected users worldwide, blocking access to emails and calendars. The issue began early on September 11, 2025, and was resolved around 2:00 AM on September 12, 2025. The root cause was identified as a specific software build version causing repeated database dismounts and failovers, leading to increased CPU utilization and message queue buildup. The outage impacted users across North America and other regions, affecting access to Teams, Outlook, and Hotmail. Microsoft implemented configuration changes to mitigate the issue and restored most of the degraded infrastructure.

Timeline

  1. 11.09.2025 22:43 📰 1 articles · ⏱ 1d ago

    Microsoft Exchange Online outage affecting global users

    On September 11, 2025, Microsoft identified an Exchange Online outage affecting users worldwide, particularly in North America. The issue began early in the morning and prevented users from accessing emails, calendars, Teams, Outlook, and Hotmail. Microsoft implemented configuration changes to mitigate the issue and restored most of the degraded infrastructure by 2:00 AM on September 12, 2025. The root cause was determined to be a specific software build version causing repeated database dismounts and failovers, leading to increased CPU utilization and message queue buildup.

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